False twisting method and apparatus



Sept. 7, 1965 L. VAN ASSENDELFT 3,204,398

FALSE TWISTING METHOD AND APPARATUS Filed Sept. 4, 1962 FIG. 1

FIG. 2

INVENTOR. LEENDERT VAN ASSENDELFT BY w M ATTORNEY United States Patent3,204,398 FALSE TWISTING METHOD AND APPARATUS Leendert van Assendelft,Arnhem, Netherlands, assignor to American Enka Corporation, Enka, N.C.,a corporation of Delaware Filed Sept. 4, 1962, Ser. No. 221,238 Claimspriority, application Netherlands, Sept. 12, 1961, 269,191 8 Claims.(Cl. 5777.3)

This invention relates generally to a method and apparatus for falsetwisting running yarn and more particularly to a method and apparatus inwhich false twist is imparted to the yarn by causing it to be slidinglywrapped around a rapidly rotating member, said member preferablyrotating around a vertical axis.

It is known that a false twist can be imparted to running yarn bycausing it to be rotated along its axis using various types of falsetwist spindles. False twist is often applied for crimping filamentyarns, the yarn being subjected to a setting treatment while in a stateof high twist. Although the yarn, after passing through the falsetwisting device, returns to an untwisted state, it retains a tendency tocrimp as a result of the setting treatment. In order that the falsetwisting process may be carried out economically, the apparatus usedshould be extremely simple and inexpensive, require little power and beeasily maintained. Moreover, the apparatus should be capable of highspeeds and be simple to operate.

With known methods and apparatus the obstacle which has always limitedsimplification and speeding up of production and reduction in costthereof is the problem of supporting the rapidly rotating member. Themember must be supported both radially and axially. From pastexperience, the axial bearing has always presented the greatestdifficulties. In the known apparatus the axial bearing usually compriseseither ball bearings, roller bearings, or gas bearings. Alsoconstructions have been proposed in which a false twisting spindle isprovided with grooves for receiving the rims of support wheels, thusholding the spindle from both radial and axial movement. All of themethods are either costly, or do not always permit the high speedsdesired. Moreover, even if high speeds are attained, the apparatus wearsout extremely fast.

Therefore, it is an object of this invention to provide a method andapparatus for false twisting yarn that does not have the disadvantagesof the prior art methods and apparatus.

Another object of this invention is to provide a method for falsetwisting yarn that will permit high production speeds and is notexpensive to operate.

Still another object is to provide an apparatus for false twisting yarnthat is simple to operate, inexpensive to construct, capable of highspeeds and subject to little wear.

A further object is to provide a false twisting apparatus that does notrequire the aid of conventional type bearings for axial support.

A still further object is to provide a method for axially supporting afalse twisting apparatus without the aid of conventional bearings.

These and other objects will be apparent from the following detaileddescription.

The invention comprises axially supporting the false twisting devicesolely by means of the running yarn. This is accomplished by passing theyarn diagonally from the rapidly rotating member or false twistingdevice to a fixed coaxially positioned thread guide such that at leaston the end of the rapidly rotating member that tends to move under thecombined influence of its weight and the yarn tension the path of theyarn between the thread guide and rotating member runs at an obliqueangle with the axis of rotation, the radial component of which is of thesame magnitude as is the axial component. As a result of the yarnrunning in such direction and because it is wrapped around the rotatingmember, said member assumes a stable position of axial suspension duringoperation. Thus, there is no need for conventional bearings to maintainthe rotating member in an axial position, the axial support beingprovided by the running yarn itself. This is an unusual and unexpectedphenomenon.

To explain this phenomenon, the forces between the rapidly rotatingmember and the yarn passing around it must be considered. It was foundthat by the method of this invention the resultant force exerted by theyarn on the rapidly rotating member may at any time be resolved into twocomponents. One of the components, which is resolved in axial direction,appears to always be in equilibrium with all the other forces acting inaxial direction on the rotating member, such as its own weight, etc. Theforce component perpendicular thereto and towards the axis has aconstant magnitude, with its direction rotating at the same speed in thesurrounding space as the rotating member. As a result of the high speedat which this force component moves, it is substantially impossible toupset the position of radial equilibrium of the rapidly rotating member.A surprisingly, additional advantage is that this method of suspensionappears to have a stabilizing effect on the yarn tension. Fluctuations,if any, in the tension of the running yarn are counteracted by smalldisplacements of the rapidly rotating member. These small displacementsare accomplished by changes in the total angle of wrap of the yarn andconsequently by an increase in tension of the Wrapped yarn.

The false twisting device used in carrying out the method of thisinvention comprises a rotatable member that can move in longitudinaldirection, near at least one end of which a fixed thread guide iscoaxially positioned. The first and last contact points on the wrappingsurface of the rotatable member are positioned much farther from theaxis of rotation than is the inner surface of the thread guide. By thuspositioing the wrapping surface relative to the thread guide, the yarnis caused to travel to said guide along the desired path forming anoblique angle with the axis of rotation.

Obviously, a fixed thread guide may be provided near both ends of therotatable member. It has been found that this is not always necessary,particularly if the apparatus is provided with a known type of radialbearing. However, if it is also possible for the rotatable member tomove transversely the requirements are somewhat different. Generally, insuch case it is not possible to use a conventional type mechanical drivesystem. With an embodiment of this type the rotatable member is formedby the short circuit armature of an electric motor. The armature isactuated without being in mechanical contact with any driving means. Inthis case, the rotatable member is supported axially by the wrappedyarn. Displacement of the armature transverse to the axis of rotationand out of the position of equilibrium results in a change in the pathof the yarn, as a result of which the armature is returned to itsposition of equilibrium. It has been found that this type of falsetwisting device is far less sensitive with regard to correct balancingof the rotatable member than is any other known false twisting device.Apparently, this is because the rotatable member will always tend torotate about a main axis regardless of its shape.

A preferred embodiment of the short circuit armature is obtained if itis shaped like a ring. The path of the yarn between the two threadguides is chosen so that at one point the yarn is wrapped around thering one or more times.

The false twisting device may also advantageously be constructed so thatthe rotatable member is supported radially with the aid of known means.With this embodiment, a fixed thread guide is necessarily only near oneend of the rotatable member which under certain circumstances simplifiesthreading the yarn. The apparatus, if provided with a known radialbearing, can then be placed in a position other than that in which theaxis of rotation is vertical. For instance, if the axis of rotation ishorizontal, the weight of the rotatable member is entirely supported bythe radial bearing, so that no radial displacement takes place. 1

The embodiments of the apparatus may be mounted on most knovm types offalse twisting devices without requiring drastic modification. In oneembodiment the drive system comprises at least one blow pipe :and therotatable member is provided with blades. The apparatus is driven withthe aid of compressed air or some other gas under pressure. Such anembodiment may be used in combination with radial gas bearings.

In a much simpler construction the rotatable member comprises a tubularspindle, the axis of which coincides with the axis of rotation, thespindle being supported radially by freely rotatable supporting discs.In this case, it is advantageous to drive the spindle mechanicallyinstead of by compressed air. F or example, there are two pairs ofsupporting discs, each pair of which forms a wedge-shaped space, thetubular spindle being kept in these wedge-shaped spaces by a drivingbelt which runs in contact with said spindle.

The tubular spindle is provided at one end with a wrapping surface.Thus, attached to said tube may be one or more radially directed armshaving thread guides at their end-s. With this apparatus, the yarn issuccessively passed through the tube, along an arm, through a threadguide, and then through the coaxially positioned fixed thread guide. Avery suitable device for accurate mass production comprises a tubularspindle having an expanded end provided with a number of symmetricallypositioned passages. The yarn is threaded into the tube, passed one ormore times through the passages, thus being wrapped around the edge ofthe expanded end and then fed to the fixed thread guide.

For purposes of illustration and not by way of limitation, the inventionwill now be described with reference to the accompanying drawings,wherein- -FIGURE 1 is a view in vertical section showing a falsetwisting spindle which is supported'by the yarn axially.

FIGURE 2 is a side view partly in section of another rapid rotary motionand is held in suspension above the plate-shaped thread guide 6.

The function of grooves 4 is twofold. First, they ensure that the yarn 1is taken along by the ring so that it does not roll over the surface ofthe ring, thus preventing loss of twist. 'Second, they serve to preventthe yarn from being damaged while the ring 3 is starting up and still incontact with the plate 6. The tensional forces in the yarn keep the ring3 in equilibrium vertically. It has been found that this state ofsuspension equilibrium can be retained even if the false twisting deviceis placed in a somewhat inclined position.

Referring now to FIGURES 2 and 3, there is shown respectively a sideview, partly in section, and a plan view of a different embodiment ofthe false twist device of the invention. The numeral 7 refers to atubular false twist spindle, .a large part of the outer surface of whichis cylindrical. The spindle is flared at its lower end. In the flaredend 8 there are four passages 9 symmetrically arranged. Near the lowerend of the spindle 7 and coaxial therewith there is a fixed thread guide10. Yarn 1 is successively passed through the tubular spindle 7, throughone of the passages 9, and through the thread .guide 10. The yarn supplyand discharge systems (not shown) are identical with those of the falsetwisting device shown in FIGURE 1. Alternatively, yarn 1 may be passedthrough several of the passages 9 before being led to the thread guide10.

The false twist spindle 7 is set in rotary motion by belt '11 moving incontact with the spindle at a very small angle, as a result of which thespindle is held from radial movement. The radial bearing comprises foursupporting wheels, only three of which are shown, '12, 13 and 16,coupled in pairs, each pair forming a single freely rotatable system.The supporting wheels 12 and 13 are coaxially coupled by bushing 14. Thebushing 14 is supported by a holder 15 such that it is freely rotatable.Similarly, supporting wheel 16 is coaxially coupled with anothersupporting wheel (not shown) by means of a bushing -(not shown), saidbushing being supported in the same manner as bushing 14. The twosystems together form the wedge-shaped spaces between the supportingwheels, in which the spindle 7 fits. In these wedge-shaped spaces thespindle 7 is pressed against the supporting wheels by the belt 11.

In FIGURE 2 are designated three yarn points A, B, and C. At point A theyarn first comes into contact with the spindle. At point B the yarn runsin vertical direction before leaving the spindle, and at point C theyarn leaves the spindle surface. Since the supporting wheels and thebelt '11 can only exert forces on the spindle which are directedtransverse to the axis of rotation thereof, the

tensional forces in the yarn, at the points of first and last contactwith the spindle, are the only external forces grammatically. Themagnets are positioned so that within the circle encompassed by them arapidly rotating electromagnetic field is maintained. Inside the circlethere is a metal ring 3. As a result of the eddy currents induced inthis ring by the rotating magnetic field a torsional moment is exertedon the ring. At diametrically opposite points two radially directedgrooves 4 are provided on the lower side of the ring 3.

Coaxial with the circle of coils 2 and on each side thereof arepositioned thread guides 5 and 6, the latter forming the bottom of acylinder with the coils 2 forming the side. Ring 3 lies on guide 6 whilein a state of rest. The y-arn 1 passes through the thread guide 5,wrapped at least once around the ring 3 in one of grooves 4 andsubsequently discharged through the thread guide 6. When the yarn ismoved .by supply and discharge mechanisms (not shown) and the coils 2excited, the ring 3 is set in which can counter-balance the weight ofthe spindle. This is in contrast with known false twisting devices inwhich the yarns runs substantially parallel to or along the axis ofrotation of the spindle.

FIGURE 4 diagrammatically shows the tensional forces acting in the yarn1 at the points A and C. The tensional force at A is indicated by P andat B by P The path of the yarn leaving the spindle at point C makes anangle at with the axis of the spindle. Therefore, the tensional force atpoint C has a magnitude of P .e where f is the coefiicient of frictionof the yarn over the spindle, and e the base of the natural logarithm.The force P .e can be resolved into an axial componentand a radialcomponent'directed towards the spindle axis, the components having amagnitude of P .e .cos 0c, and P .e .sin 0c, respectively. If the weightof the spindle is G, then the following relation holds for the verticalequilibrium thereof:

When the yarn runs practically parallel to or along the axis of thespindle, as in the known false twisting apparatus, the angle a. is andthe above-mentioned equation consequently becomes:

Since P is always greater than P it is obvious that the known apparatuscannot operate without an axial bearing since the latter equation cannotbe satisfied. However, it should be added that with known false twistingapparatus, the yarn can run upward in which case the yarn tensions canbe adjusted so that the equation P -P +G:0 is satisfied. Nevertheless,even in this case axial support is necessary since the apparatus is notvery stable.

In the false twisting device of this invention, the spindle ispractically always in axial equilibrium since the function e .cos a.decreases continuously as on increases from 1 to 180 and becomes 0 wheno :90. Thus, the abovementioned mathematical relation is satisfied.

The apparatus of FIGURES 2 and 3 may also be advantageously used in aposition in which the axis of spindle rotation is horizontal. When thespindle is in this position, the following relation holds for the axialequilibrium:

For the yarn (shown in FIGURE 2) passing through the apparatus thisrelation may always be satisfied, irrespective of the values of P and PThe mathematical relations describing the equilibrium of forces alsoshow that this equilibrium is stable. This accounts for the spindleautomatically taking up its proper position at the beginning of theprocess.

It should be added that, in addition to the aforementioned axial forces,a torsional moment, and a transverse force having a magnitude of P .e".sin or act on the spindle. However, said torsional moment and forcechange direction twice every revolution. Owing to the high speeds of thespindle, i.e. up to 200,000 revolutions per minute, said moment and saidtransverse force cannot upset the position of spindle equilibrium.

The setting treatment of the yarn, if it is to be crimped by the falsetwisting process, consists of softening and subsequently hardening theyarn in a known manner while it is in a state of high twist. With yarnmade from a thermoplastic material, the setting process may consist ofsuccessive heating and cooling of the yarn.

While the invention has been illustrated by the foregoing specificexamples, it will be apparent to those skilled in the art that it may beused with many different types of false twist devices and other twistingapparatus and that numerous modifications, variations and embodimentswithin the scope of the invention are possible. Therefore, the inventionis intended to be limited only as set forth in the following claims.

What is claimed is:

1. A twisting device comprising a rotatable member capable of axialdisplacement provided with at least one yarn wrapping means, means fordriving said member, and a thread guide means coaxially positionedadjacent one end of said member, said yarn wrapping means disposedfarther outside the axis of rotation of said member than the threadguide means whereby the path of yarn passing from said rotatable memberto said fixed thread guide runs at an oblique angle with the axis ofrotation of said member to support said rotatable member in the axialdirection solely by means of the yarn.

2. A false twisting device comprising a rotatable tubular spindle flaredat one end, means for driving said spindle, passage means in said flaredportion of said spindle for slidably wrapping yarn therethrough, and afixed coaxially positioned thread guide means adjacent said flaredportion whereby the yarn path from said passage means in said flaredportion to said thread guide means forms an oblique angle with the axisof rotation of said spindle to support said spindle during rapidrotation solely by means of the running yarn.

3. The false twisting device of claim 2 in which the spindle is radiallysupported by means of two pairs of supporting discs, said spindle heldin position against said discs by means of a driving belt.

4. The false twisting device of claim 2 in which the wrapping meanscomprises a plurality of symmetrically positioned passages.

5. A false twisting device comprising a rotatable tubular member flaredat one end and adapted for the passage of yarn longitudinally throughits center, rotatable elements to support said member against radialdisplacement, drive means to impart rotation to said member and forurging it into contact with said rotatable elements, yarn passage meansin the outer periphery of said flared portion of said member, and athread guide means positioned coaxially with said member and adjacentthe flared portion whereby the yarn after it passes through said memberand said passage means runs at an oblique angle with the axis ofrotation of the member to support said member during rapid rotationsolely by means of the running yarn.

6. The false twisting device of claim 5 in which the rotatable member issupported radially by at least two pairs of discs rotatable about spacedaxes, the discs of each pair overlapping to form a throat for receivingsaid tubular member and in which said drive means comprises an endlessdrive belt.

7. In a method of axially supporting a rotatable fluted tube, the flutedend portion of the tube having perforations in the wall thereof, thesteps of (a) passing a thread into the tube and along the rotationalaxis, thereof,

(b) directing the thread radially outward through one of saidperforations to slidably engage the outer rim of said fluted portion;and

(c) passing the thread from said rim through a thread guide positionedadjacent said fluted end portion and located on the axis of rotation ofthe tube whereby an oblique angle is created by the thread path and theaxis of rotation.

8. A method of axially supporting a rotatable yarn twisting membersolely by means of the yarn being twisted thereby, which comprises thesteps of (a) passing a yarn along the axis of rotation of said member,

(b) displacing the yarn radially from said axis to a yarn grippingposition located on said member, and

(c) passing the yarn from said gripping position to a coaxiallypositioned thread guide whereby an oblique angle is created by the yarnbetween the yarn path thus created and the axis of rotation.

References Cited by the Examiner UNITED STATES PATENTS 3,035,399 5/62Scragg 5777.3

FOREIGN PATENTS 1,190,688 10/59 France.

775,075 5/57 Great Britain. 775,076 5/ 57 Great Britain. 786,580 11/57Great Britain. 807,529 1/ 59 Great Britain. 815,650 7/ 59 Great Britain.

MERVIN STEIN, Primary Examiner.

1. A TWISTING DEVICE COMPRISING A ROTATABLE MEMBER CAPABLE OF AXIAL DISPLACEMENT PROVIDED WITH AT LEAST ONE YARN WRAPPING MEANS, MEANS FOR DRIVING SAID MEMBER, AND A THREAD GUIDE MEANS COAXIALLY POSITIONED ADJACENT ONE END OF SAID MEMBER, SAID YARN WRAPPING MEANS DISPOSED FARTHER OUTSIDE THE AXIS OF ROTATION OF SAID MEMBER THAN THE THREAD GUIDE MEANS WHEREBY THE PATH OF YARN PASSING FROM SAID ROTATABLE MEMBER TO SAID FIXED THREAD GUIDE RUNS AT AN OBLIQUE ANGLE WITH THE AXIS OF ROTATION OF SAID MEMBER TO SUPPORT SAID ROTATABLE MEMBER IN THE AXIAL DIRECTION SOLELY BY MEANS OF THE YARN. 